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Jan 11 2018

What is high availability (HA)? Definition from

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high availability (HA)

In information technology, high availability refers to a system or component that is continuously operational for a desirably long length of time. Availability can be measured relative to 100% operational or never failing. A widely-held but difficult-to-achieve standard of availability for a system or product is known as five 9s (99.999 percent) availability.

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Since a computer system or a network consists of many parts in which all parts usually need to be present in order for the whole to be operational, much planning for high availability centers around backup and failover processing and data storage and access. For storage, a redundant array of independent disks (RAID ) is one approach. A more recent approach is the storage area network (SAN ).

Some availability experts emphasize that, for any system to be highly available, the parts of a system should be well-designed and thoroughly tested before they are used. For example, a new application program that has not been thoroughly tested is likely to become a frequent point-of-breakdown in a production system.

This was last updated in September 2005

Next Steps

Read about the HP XP7 Storage SAN array. which offers high-availability for virtualized data centers with large storage needs.

Related Terms

infrastructure (IT infrastructure) Infrastructure is the foundation or framework that supports a system or organization. In computing, infrastructure is composed of. See complete definition motherboard A motherboard is the main printed circuit board (PCB) in a computer. The motherboard is a computer’s central communications. See complete definition power cycling Power cycling is the process of turning hardware off and then turning it on again. In the data center, technicians use power. See complete definition



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